This invention relates to a split system master cylinder having compansator valves which close simultaneously to permit the development of substantially identical first and second hydraulic operating pressures to synchronize braking of the front and rear wheel brakes of a vehicle.
Most vehicles currently being produced are equipped with disc brakes on the front wheels and drum brakes on the rear wheels. The front wheel disc brakes require very little initial actuation pressure from a master cylinder, whereas substantial initial actuation pressure is required to move brake shoes into engagement with the brake drum on the rear wheel drum brakes. In order to achieve simultaneous actuation between the drum brakes on the rear and disc brakes on the front, a metering valve is required to delay the communication of braking pressure to the disc brakes until the drum brakes are actuated.
In order to meet proposed stopping distance requirements established by the Department of Transportation, it has been suggested that disc brakes be placed on both the front and rear on vehicles. A cost saving could be achieved from such a braking system if the metering valve was eliminated. Unfortunately, split system master cylinders, such as the master cylinder disclosed in U.S. Pat. No. 3,818,700, do not initially develop the same hydraulic pressures in the separate pressurizing chambers which supply the front and rear wheel brakes with actuating fluid. In such master cylinders, sequential movement of a first piston closes a first tilt valve to develop a first pressure force in a first chamber, and thereafter, the first pressure force and a resilient member move a second piston to close a second tilt valve and develop a second pressure force in a second chamber in the master cylinder. Thus, there is always a delay in the initial communication of the pressurized operating fluid supplied to the brake system connected to the second chamber.